The invention relates to a positioning arrangement for a meeasuring-value sensor, which is secured at one end of a guide tube, through which a lead connected to the measuring-value sensor extends to an evaluation unit and whose other end is coupled to a fixedly arranged screw device serving to displace the guide tube in the longitudinal direction.
Such positioning arrangements serve, for example, to carry out speed measurements or oscillation measurements on inaccessible rotating parts of a machine. The positioning arrangement mentioned in the opening paragraph is known from the prospectus "21 001 Proximity Probe Housing Kit" of the Company Bently, Nevada, U.S.A. In this case, a housing accommodating a screw device serving for the longitudinal displacement of a guide tube is secured to the machine at an accessible area. The guide tube has at one end an external thread and has at its other end a measuring-value sensor. The measuring-value sensor is taken to the rotating part of the machine by longitudinal displacement of the guide tube. For longitudinal displacement, the guide tube is screwed in a nut which is secured in the housing and has an internal thread matching with the external thread of the guide tube. The measuring-value sensor is connected through a lead extending in the guide tube to an evaluation unit outside the housing. Upon rotation of the guide tube (longitudinal displacement), the lead must be detached from the evaluation unit in order that no rotation of the lead and hence no destruction of the lead takes place. As a result, the operation of adjusting the measuring-value sensor becomes complicated. Moreover, additional plug contacts must be provided.